This invention relates to railroad hopper cars and particularly to a pneumatic outlet gate therefore. Hopper car outlet gates are located on the bottom of the car body. They include slanted bottom walls known as slope sheets. The slope sheets are bounded by end walls. The slope sheets have a gap between them at their lower edges forming a discharge opening. Beneath this opening there is attached a circular discharge tube with an arcuate valve member in it. The discharge tube extends through end walls where it can be connected to vacuum hoses for unloading purposes. The valve member is mounted for rotation in the end walls. The valve can be rotated between open and closed positions where it alternately permits or blocks flow of granular materials through the discharge opening and into the discharge tube. Outlet gates of this general type are exemplified by U.S. Pat. No. 3,778,114, the disclosure of which is incorporated by reference.
Hopper cars are used to transport granular products such as grain, sugar, and plastic pellets. Small amounts of such materials have a tendency to get stuck or caught in a car rather than flow out during unloading. Any corner or crevice becomes a trap for small grains or pellets. The outlet gate valve is a particularly likely place for individual grains to get trapped between the movable valve member and the discharge tube. This leads to the ever present problem in hopper car operations of cleaning a car of all remnants of a load before filling it with a new load. If any such remnants are present, they contaminate the new load. This cannot be tolerated.
While the car compartments have been designed to eliminate corners, ledges or joints where granular materials can become trapped, the outlet gate has been a continuing source of difficulty in assuring complete removal of lading. As mentioned above, remnants of a load tend to get trapped or wedged between the arcuate valve member and the discharge tube. This occurs because the lateral or side edges of the open valve member are permitted to take up a position where, together with the internal wall of the discharge tube, they form a small receptacle which is, in essence, concave upwardly. Lading naturally gets caught in this receptacle. If only a small amount of lading is so trapped it may be possible to crush or pulverize the particles upon subsequent closing of the valve. However, just because it is possible to close the valve does not mean the discharge tube is clean. Further, it sometimes happens that so much material is caught that the valve seizes and cannot be closed.
The prior art solution is to disassemble the outlet gate valve upon every unloading. With the valve element removed the discharge tube can be vacuumed out and inspected to assure total removal of all material. While this method is serviceable if performed correctly, the cost in labor and time is significant. What is needed is an outlet gate that can be totally cleaned without having to remove the valve member from the discharge tube.